the effect of salinity stress on growth parameters and essential oil percentage of peppermint (mentha piperita l.)

peppermint (mentha piperita l.) is one of the most important plants producing essential oil. an experiment was carried out using a randomized complete block design with 3 replications to study the effect of salinity stress on growth parameters, essential oil percent of peppermint. 4 levels of salinity solution containing 0, 50, 100 and 200 mmol nacl was applied in irrigation plantings in a greenhouse. the results showed that salinity stress significantly affected  stem  length,  root length, shoot wet weight, root wet weight and shoot dry weight, root dry weight, internodes length, biomass and essential oil percent in p < 0.05. an increase in the salinity lead to reduce in length of stem and root, fresh weight of stem and root, dry weight of stem and root, internodes length, total  biomass and essential oil percent. it is necessary to mention that peppermint did not tolerate 200 mmol nacl and died under this condition. the highest values  of  growth parameters  and essential 1 oil percent were observed under non-salinity condition(control). also, were increased proline with the increase of salinity( p < 0.05)